aC CALORIMETER FOR DETERMINING 
THE HEATS OF REACTION AT | 
HIGH TEMPERATURES | 


BY 


LOUIS 7 NEES 
B. S. College of the City of New York, 1918 
M.S. University of Illinois, 1921 


THESIS 


| the the JOURNAL OF THE eae CERAMIC SOCIETY, 
| Vol. 6, pages 1268-1298. 








ABSTRACT 


Apparatus.—A vacuum calorimeter containing an insulated platinum resistance 
furnace is described for use in determining reaction heats, and the heat absorbed in 
raising the temperature of a material in the furnace from room temperature to 1200°C, 
and also the heat evolved in cooling down the material from 1200°. 

Materials experimented with.—Four typical clays are employed, namely A-1 
English china clay, North Carolina kaolin, Tennessee ball clay No. 5, and Laclede- 
Christy raw flint clay. The calorimeter is calibrated with pure quartz. 

Results.—The numerical data obtained are assembled in TableIV. The quantity 
of heat absorbed per gram per degree on heating the air dried clays over the complete 
temperature range 25—1200° amounts to 0.50—0.55 calories, whereas the heat evolved 
on cooling the final products per gram per degree through the range 1200-700° is 
0.23-0.29 calories. 

The heat absorbed in the ranges 24-420°, 420-900°, and 900-1200°, together with 
the heat evolved in the ranges 1200—900°, and 900—700°, are also given for all of the 
above clays. 


I. Introduction 


1. Purpose of the Investigation.—When refractory materials are fired, 
heat is absorbed, the net quantity depending upon the specific heats and 
upon the heats of reaction resulting from chemical and physical changes 
in the constitution of the fired material. Exothermic reactions help to 
raise the temperature of the materials whereas endothermic reactions re- 
quire an additional amount of heat to complete them, before the tempera- 
ture can again rise. In materials like clays, and in bodies containing 
them, these reactions are quite often not reversible, meaning that the heat 
absorption on firing is not equivalent to the heat evolution on cooling. 
It is impossible then, with such materials to obtain the heat absorption 
on firing by the method of mixtures, which is the usual method employed 
for determining specific heats. 

In the method of mixtures, the substance is heated to a high tempera- 
ture, and the resulting heated material is dropped into a calorimeter, and 
the heat evolved by the material measured by the increase in temperature 
of the calorimeter bath. ‘The present investigation has primarily for its 
purpose the measurement of the heat energy required to raise the tempera- 
ture of raw clays, from room temperature to 1200°C, by a method and ap- 
paratus devised for the work. An experiment is run continuously on one 
sample to the highest temperature, and the heat absorption is measured 


’ 


4 


for three separate ranges of temperature; then the energy source is cut 
off, and the heat evolved by the fired material as it cools to 700° is measured 
over two ranges of temperature. 

All temperatures given in this paper are in degrees centigrade. 

2. Data in Literature on Specific Heats of Minerals, Refractories and 
Clays.—These are all data on materials experimented with by the method 
of mixtures. ; 

(a) Minerals. White! obtained the Interval Mean Specific Heats 
on the silica minerals, quartz and cristobalite, on the feldspars, anorthite, 
andesine, albite, microcline, and on other natural minerals as pseudo- 
wollastonite, and on some of the natural forms of magnesium silicate. 
White also worked with some of the glasses of the above materials. His 
range of temperature was from room temperature to 1400°. From the 
data, he calculated the true instantaneous specific heats at different tem- 
peratures. His data will be referred to later. 

Wietzel? found the Interval Mean Specific Heats of cristobalite, quartz, 
chalcedony and silica glass up to 1400°. ‘The data on quartz and cristo- 
balite are discussed in a later chapter. 

(b) Refractories. Bradshaw and Emery® fire obtained the Interval 
Mean Specific Heats on some refractory materials up to 1400°. TableI | 
gives their results in calories per gram from ¢° to 25°. 


TABLE I 
INTERVAL MEAN SPECIFIC HEATS OF REFRACTORY MATERIALS ?° To 25° 
Silica ; Fire Pure - Stourbridge 

# brick brick zirconia fire brick 
600 0.226-8 0.228 02137 0.227 
1000 .263-2 .265 PLOY, . 263 
1200 292-0 284 WNC, 202 

1400 293-5 .297 es: ot, 


Tadokoro‘ experimented with different types of brick to 900°. The 
Interval Mean Specific Heats in calories per gram from #° to 30° are given 
in Table II. 

Moore’ worked with a terra cotta body that had been burned to 1100°. 
In cooling from ¢° to 0°, when ¢° is equivalent to 500°, 700° and 900°, 
the Interval Mean Specific Heats in calories per gram are 0.235, 0.245 and 
0.249, respectively. 

1W. P. White, Amer. Jour. Sci., 47, 1-43 (1919). 

* Rudolf Wietzel, Z. anorg. allgem. Chemie, 116, 80 (1921). 

*L. Bradshaw and W. Emery, Trans. Ceram. Soc. (Eng.), 19, 84-92 (1919-20). 

* Yoshiaki Tadokoro, Sci. Repts. (Téhoku Imp. Univ.), 10, 339-410 (1921). 

5 J. K. Moore, ‘“‘Tests on the Thermal Conductivity of Terra Cotta Fireproofing,”’ 
Thesis for B.S. Univ. Tl. (1908). 


o 


TABLE II 
INTERVAL MEAN SPECIFIC HEATS OF BrIcK, t°® To 30° 
je Magnesia Red clay Silica Chrome Shamotte 
218 0.223 0.207 0.199 0.178 0.197 
303 . 238 221 .218 .195 . 209 
382 254 . 239 238 .210 222 
480 . 263 .247 246 .216 . 238 
579 . 266 . 249 .249 La 251 
687 .265 .247 . 250 .219 . 255 
796 . 264 . 242 .247 2218 . 249 
894 .263 BAY . 242 215 .241 


(c) Clays. Knote! determined the specific heat of a flint clay from 
Olive Hill, Kentucky, from 150° to 22°. The raw clay had a specific 
heat of 0.237, the clay burned to 650°, a specific heat of 0.204, and when 
burned to 1050°, a specific heat of 0.200. 

3.. Method, General Description—vThe method employed consisted 
of immersing in a thermostat at room temperature a small vacuum jacketed 
furnace containing the sample of material to be investigated. The furnace 
was heated electrically by means of a platinum heating coil and the energy 
supplied in this way was accurately measured by means of a recording 
wattmeter. A thermocouple was inserted in the center of the charge for 
reading its temperature. ‘The whole furnace was encased in a nickel 
cylinder which was evacuated, the whole being immersed in the water of 
the stirred bath. 

During the passage of the heating current, some of the energy supplied 
to the furnace leaked out through the nickel containing cylinder into the 
water of the bath. This tended to raise its temperature above that of 
the room, In order to prevent this and to measure the energy which 
leaked out in this way, ice water was admitted to the bath at such a rate 
as to keep its temperature practically constant. An equivalent amount 
of water from the bath overflowed and was collected in a container for 
weighing. When, with a given heating current, the temperature of the 
center of the charge became constant and remained so for some time, this 
temperature was read and the container which received the overflowing 
water was removed and replaced by a second container. The heating 
current was then immediately raised to the second level and the above 
procedure repeated, as soon as the temperature of the center of the charge 
had again become constant at the higher value. 

By weighing the water which overflowed from the water bath, the 
amount of energy which leaked out of the furnace through each stage 
could be accurately computed. From the record of the wattmeter, the 
amount of energy sent into the furnace could be similarly accurately 


1 J. M. Knote, Trans. Amer. Ceram. Soc., 14, 394-8 (1912). 


6 


computed. ‘The difference between these two amounts obviously repre- 
sents the heat absorbed by the charge and the furnace parts. The heat 
was measured with an accuracy of about 1% in the present investigation. 

In order to determine the amount of heat absorbed by the furnace parts 
during the operation, the same series of experiments was repeated, using 
in place of the charge of clay a charge consisting of a known weight of 
quartz whose specific heat curve up to high temperatures has been ac- 
curately determined. In this second series of experiments, the heat ab- 
sorbed by the ee is known and by subtracting this from the total heat 
Les. absorbed by the furnace plus 

eS the charge, the heat taken up 
AA by the furnace parts could be 
! computed. By combining this 
on ee value with the results obtained 
when using the various clays in 
the furnace, the heats absorbed 
by the clays themselves can 
obviously be calculated. It is 
estimated that this heat was 
Sealhah yO measured with an accuracy of 
about 10%. 

It was found expedient to 
limit the temperature ranges to 
approximately 24-420°, 420— 
900°, 900-1200° for ascending 
temperatures, and 1200-900°, 

100 300 500 700 mens00 Magog w/A00 a OU 700° for elseonestty tem- 
Degrees Centigrade peratures. 
Fic. 1.—Average USSU heats between 0° and 4 Available Specific Heat 
ate Data for Calibrating the Cal- 
orimeter.—The only data that are given on pure materials and over the com- 
plete range of temperatures from 0° to 1400° are those furnished by the ex- 
periments of White! and Wietzel.? The list of materials contains feldspars 
and magnesium silicates, which however are difficult to obtain with theo- 
retical compositions. ‘The glasses of these minerals crystallize fairly easily, 
which decreases their value for calibration purposes. ‘The only other 
materials that can be considered are, then, quartz and cristobalite, data 
being furnished by both experimenters. Figures 1 and 2 give the com- 
plete data. 

It will be noticed that the data on the quartz are much more concordant 

than are the data on the cristobalite. Wietzel has shown, as have others, 


1W. P. White, loc. cit. 
2 Rudolf Wietzel, loc. cit. 














0.250 

















Calories per Gram 
2 
hs 
S 





0.2/0 











Pa ne ea Eee a 


[i 
bead 
EI 
ke 
Ea 
S| 
| 
ie 
: 








" 


as Washburn and Navias,! that the physical properties of cristobalite 
depend on the previous history of the material, that is, of preparation and 
of the extent of calcination. 

For quartz, White gives values only up to 1100°, whereas Wietzel gives 
them as high as 1400°. In a preliminary run of the present investiga- 
tion, crushed quartz heated to 1400°, in eight hours, gave inversion 


to cristobalite of about one ee: 
quarter of the material. In ; — et 
two regular runs, quartz heated y za aim 

pac mel 


to 1200°, in ten hours each, 
gave no trace of inversion. 
This was determined by measur- 
ing the index of refraction of 
the grains. As the maximum 
temperature to be attained 
safely in the calorimeter is 
1200°, quartz may be used to 
acd vantace: = By ad ding 
Wietzelisa result sat: 212008 to 

















Calories per Gram 


Whites res ults 


those of White’s at lower tem- . Wretzels resu/ts on sample 
calcined to 1000 °C. 
peratures, the data are com- Wietzel$ resu/ts on sample 


calcined to 11/00°C. 


plete for application to the 
present problem. As the work 
of White has extended over 
many years and with concor- 


dant results, preference has py. 2.—Average specific heats between 0° and 
been given to his work. t° of cristobalite. 





100 300 500 700 900 1/1/00 1300 
Degrees Cen tigrade 


II. Heats of Reaction of Clays at High Temperatures 


5. Clays Experimented with.—The clays experimented with are typical 
of the different kinds used in the industries. Unfortunately the choice 
had to be limited to the purest clays, on account of the conditions under 
which the experiments were made. Attempts to experiment with brick 
clays and the like, have resulted in wrecking of the furnace, due to the - 
bloating of the clays. The chemical analyses of the clays are given in 
Table III. 

6. Reactions in Clays Due to Heating.—Mellor and Holdcroft,? work- 
ing with kaolinite, determined from their time-temperature curves ob- 


1 Edward W. Washburn and Louis Navias, Jour. Amer. Ceram. Soc., 5, 565-85 
(1922). 

2J. W. Mellor and A. D. Holdcroft, Trans. Ceram. Sot. (Eng.), 10, 94-120 
(1910-11). 


S 





TABLE III 
CHEMICAL ANALYSES OF THE CLAYS EXPERIMENTED WITH 
(1) (2) (3) (4) 
Per cent Per cent Per cent Per cent 
SiO2 45.20 45.2 45.60 43.70 
Al;O3 38.45 38.8 35.90 39.38 
Fe,03 0.45 0.3 1.00 0.79 
TiO, trace trace 1.00 1.95 
CaO trace 0.9 0.10 0.10 
MgO trace 8 .30 OF 
Na,O 0.00 .46 
2.1 | trace 
KO .65 J we, 
H,0 © 14.80 Meze nae a hel 
Ign. loss a 12.5 14.60 14.08 
99.55 100.6 99.68 100.37 


(1) North Carolina kaolin (Harris Clay Co., Sprucepine). 
(2) A-1 English china clay (Hammill and Gillespie). 

(3) Tennessee ball clay No. 5 (Mandle Clay Mining Co.). 
(4) lLaclede-Christy raw flint clay (Missouri). 


tained by a differential thermal method and from other experiments the 
following results: | 

(1) Just above 500°, heat is absorbed by an endothermic decomposition of kaolinite _ 
into free silica, free alumina and water. Graphically the ‘“‘latent heat of decomposition”’ 
is calculated to be 42 calories per gram of raw clay. 

(2) At approximately 800°, in the heating curve, there is an exothermic change 
shown corresponding with a physical change of the free alumina, whereby the alumina 
becomes less soluble in acids, less hygroscopic.and more dense. The “latent heat of 
transformation” is determined graphically to have the value of 21.5 calories per gram. 

(3) The formation of sillimanite in kaolinite when heated over 1200° is due to 
the recombination of the free alumina with some free silica formed at about 500°. 

Wallach,' by a differential thermal method, has shown that kaolin, 
clays, mica and glauconite absorb heat when dehydrated between 450° 
and 600°, and evolve heat between 900° and 1000°. According to Le 
Chatelier the evolution of heat is due to a transformation of the alumina. 
Wohlin? substantiates the above results by a similar method. Inclays, 
between 560° and 580°, there is an endothermic reaction, at 960° the re- 
action is exothermic. Bauxite, Al,O;.H.O, has an endothermic reaction 
at 540°, while bauxite Al,O3;.8H.O has an endothermic reaction at 310°— 
both having exothermic reactions at 1060°. 

Zoellner® heated clays to high temperatures and then disintegrated 
the products in hydrofluoric acid. The residue consisted of sillimanite 
crystals. He determined that cone 10 (ca. 1300°) had to be reached before 

1 Ruby Wallach, Compt. rend., 157, 48-50 (1913). 

2, R. Wohlin, Sprech., 46, 719-21, 733-5, 749-51, 767-9, 780-2 (1913). 

3 Zoellner, Brit. Clayworker, 22, 40 (1913). 


2 


sillimanite could be obtained, and also that the plastic clays gave only 
3-5% sillimanite, whereas the lean clays (kaolins) gave 25% under similar 
conditions of firing. 

In Fig. 3 is shown the results of a thermal analysis of North Carolina 
kaolin, determined from the time-temperature readings taken on heating 
a sample of the clay in a resistance furnace. It shows that most of 
the water of combination is 
disengaged between 535° and 


600 > : 0- North Carolina Kaolin ea. ° 


A : x - North Carolina Kaolin pent 
Satoh! has determined quali- */3 % Graphite aa 
. aon ‘ ¢ - North Carolina Kaolin 
tatively, by a very sensitive +2% Graphite 


differential method, using quartz 
sand as a comparison substance, 
the heat reactions occurring in 
a Japanese kaolinite. His re- 
sults may be summarized as 
follows 




















(1) Heat absorption up to 100°, 
due to evaporation of moisture con- 
tained in the specimen. 

(2) Weak heat evolution from 
100° to 300°, possibly due to oxida- 
tion of foreign minerals and organic 
substances. 

(3) Heat absorption from 450° 
to 650°, due to the dehydration of 
the kaolinite. O 









































f /0 20 3O 40 50 60 70 80 
(4) Heat absorption from 650° Minutes 


to 700°, due to the dissociation of 
kaolinite into free alumina and free 


Fic. 3.—Thermal analysis of North Carolina 


oa kaolin. 

silica. 
(5) Weak heat evolution near 950°, due to the polymerization of the alumina. 
(6) Weak heat evolution between 1200° and 1300°, due to the formation of amor- 


phous sillimanite by the recombination of dissociated free alumina and free silica. 


7. Evacuation of Raw Clays.—In preliminary runs the platinum 
container was filled with the powdered clay, and then evacuated in the 
system. Under these conditions, even with perfect control of the rate 
of evacuation, it was uncertain whether the clay had remained in the con- 
tainer, or had been partly expelled by the sudden expansion of gases. 
It was then found necessary to mold and press the clay, as described else- 
where, in order to keep the clay in the container. This procedure has a 
number of recommendations apart from the above-mentioned one. It 
approaches the methods used in practice, and also allows a larger sample 
to be employed—roughly from 200 to 300 grams. 

1S. Satoh, Jour. Amer. Ceram. Soc., 4, 182-94 (1921). 


10 


8. Pressures Developed by the Dissociation of Clays.—Throughout 
the experiments, the vacuum pump is kept running, and with unhydrated 
materials, the pressure is kept down to a fraction of a mm. of mercury 
throughout the run. With clays, as the temperature varies, and with 
continuous withdrawal of the water vapor by the pump, a pressure is de- 
veloped in the calorimeter depending upon the quantities of water vapor 
being expelled. These are not equilibrium vapor pressures, but they show 
relatively the velocities with which the dissociation of the clay takes place, 
as the temperature rises. Figures 4, 5, 6 and 7 show the changes in pressure 
with temperature for the clays investigated. 

In the range 0-400°, the increase in pressure between 30° and 100°, 
shows that the clays are giving off adsorbed moisture held so tenaciously 




























f| 
l/ 


ae 
ton | 

















-— ara 
a oa a 
NI Beeson 
Saacen 6 WB 
Bh snessesssnns SeenGeeseccsseescaee 
co BSEeosnSolneaa 
EEE EERE REESE EEE 
Deki neon Sie See SS ee Sees 


















BERLGE 


A | 
Ban 










































































































































































50 /00 150 200 250 300 350 400 
a Degree esmCn 
Sa a Nor RL rca a ag 
uv fl | 
NS ’ ao 
. FHA Hy BEER 
9 EE S5noce HH peeoom Ba 
9 AEH EERE EE Seeceetaesa 
(yo Ue Size H = KERS = ‘ea 2 eS Se 
See csueseseuas 
& EE FENCE RREE EERE EEEEEEEEREEEE 
G 25 4 en ON ees an a lS ado os 
| tH] + at +E +} EE ted a ee ee a 
tt bebeict fas) ae Sahel al ee ede SSSR ReSESesae 
ERE Bene eeeeeceneeueunssuscecess" 
Oo J BEE EEE EEE EEE Ed 
400 450 500 S50 600 650 700 750 800 850 900 
Degre 2 Smee 
cag ee Ee 
9 DEERE EEE EEE 
900 GS50 1000 /050 1/00 1150 /200 


Degrees (Ss 


Fic. 4.—Pressure developed by the dissociation of North Carolina 
kaolin. 


as not to be given off by the clays on drying at 110° at atmospheric pres- 
sure, or by continued evacuation at room temperatures. 

In the range 400-900°, the dehydration of the clays seems to take place 
in two stages. In the first stage, the evolution of water vapor starts 
rapidly at about 475°, developing a pressure of about 2.2 centimeters. 
This maximum is maintained while the temperature rises 100-200°, de- 
pending upon the clay. Then appears the second stage, in which the de- 
hydration velocity is suddenly lessened, but falls in a rather decisive and 
continuous manner, while the temperature rises 200-300° depending upon 
the clay. 

In the range 900-1200°, only those clays containing organic matter 
developed pressures. The Laclede-Christy raw flint clay showed only a 
slight increase in pressure, but the Tennessee ball clay No. 5 developed 


11 


a rather high pressure. The run on the latter clay through the ranges 400- 
900°, and 900-1200°, was characterized by extremely bad odors issuing 
from the vacuum pump, due to the decomposition of the organic matter 


















































































































\ Sede esses 
M Be eB HH H 
> Sel aie 
aie EEE EEE EEE EE =" H 
ae icsuezea saB na SESTSECSTaECEIC 
Saaas BREECH EEE EEE EEE EEE CRETE 
= as wt iia aaa i oa oO 
Dab fat oe ss Sib es a ea 
5 as as Siete Sos eaheteat ale ie een eae os a 
sels mea 
seas S EEE ESSE EEE ooo ee 
g ne Flom ay SS [om fone fee 
fsoia oo ace acne ol pate 
G Ee) eer CPs . oocoeee 
my pote f Zea J — a a Le CS 
me SESERoS Saeumene baal yea aem 
oases ies ed me co a a co a ll 
5 On a Se a can a 













400 450 500 550 600 650 700 750 800 850 900 
Degrees C. 





ici eer tet etree be oe ia 
GOO 95 Oe OVO (OEC an /OO 1 SOM COO 
Degrees C- 





Fic. 5.—Pressure developed by the dissociation of A-I English 



























































china clay. 

“EEE EEE ERE CERES Seecneee a 
BEES ARES SaaRe SR VARE RH Ria (ea _ 
Rene Be “ASCH neces 4 fp 

06)-EELY co —— as 

. if BSP m 

Ty ZI Pngaeae SEse PEE sce sees 
03+ ese : 
Seee : He Se 

BEREE EEE EEE EH eee 

O | TI ee) sy eaee ane geen = 
oO 50 /00 1/50 — =e 300 ae Eade 


Degrees C. 


































































































































S 7. 
20 Segee dcce enema ACC a Li -| Ease + ARR eee 
8 20 EEE EERE EH BEER EERE EEE EEEEEEEECH 
‘ Se ee eeaas = Sateen Secs sagen fe Sap aSss 
BEE E EEE RE EAE FERRER EEE EEE EEE 
= Saree meets cos ao BREE EEEEE AEH (Sl es HH mal fscecneacme 
qs fee ae enc asl lie sae a Fe pa | i picts TI 4 4 tt = 
5 PTT ttt ft asias) SEH » ft | | I Senses 
Gas Yt be Pale P+ . BS IH eat Ht 4 
: 10 pt tH [ | ee | | | ++ | [| HeBeaaae 
ri es pon = Pt tt tts Wt | | — te [fff ft tt 
opps szsszecerezcetecrcereetecsesssccz =H 
S pepe | pe atatee ts ep opiel y ats Peery Si 
a a i (a — 
: sueseeecceeeeeeas sists ST = Be 
» FEEEEEEEEE EERE ESE EERE EEE EE EEEEEH 
400 450 500 550 600 650 700 750 


Peo 
Bee 

















900 950.8 7000 Jos0™ “1/00, “1/50, 1200 
Degrees €. 


Fic. 6.—Pressure developed by the dissociation of Tennessee 
ball clay No. 5. 


present. After cooling, the clay was found to be colored black throughout. 
9. The Heat Effect of Carbon and Sulphur in Clays.—The combustion 
of one gram of carbon to carbon dioxide liberates 8080 calories of heat. 


12 


The combustion of one gram of sulphur to sulphur dioxide liberates 2240 
calories. If the clay contains an appreciable amount of these constituents, 
especially of the former, the heat effect is theoretically large. | 

From the “Paving Brick Clays of Illinois,”! the following are the 
carbon and sulphur contents of some usable clays:— 


Ki K3 Ka Ks Ky7 Ku Kis Fi ; Average 
Sin % 0:27. 0-16) 0.14. O11l [OMS 6024 0 Oe ee 
Cin % 1.44 1.50 Vaal ee is 1.01 .90 OF a Leb 


Assuming these averages for a clay, the heat given up by the complete 
combustion of the carbon and sulphur in 100 grams of clay would be: 


8484 calories 
403 calories 


For C 1.05 X 8080 
For Ss? 0718. x 2240 


8887 calories 


Assuming the specific heat of clay to be 0.70 in the range of combustion, 
400-900°, then if heat was evolved at one time, and if all of the heat went 
to raising the temperature of the clay, the sudden rise of temperature 
: would be about 125°. In 
practice, since the oxida- 
tion period extends over 
a long length of time, and 
over a wide range of tem- 
perature, such sudden in- 
creases in temperature are 
not to beexpectedm=sbue 
heat evolved, however, is 
Ss¢ 600 460 11700 +t) | pé00- a#e apo oe LAKETIGUD Dy teeta tciaa) 
H ee and its surroundings. 

maaan While obtaining the 


Degrees C. thermal analysis of the 
Fic. 7.—Pressure developed by the dissociation of | North Carolina kaolin an 
Laclede-Christy raw-flint clay. 





























GUGBET ane 
SSaG8/ 808 























































HEHE 



































Cms. of Mercury 





























‘Al 
EERE CC TEERE Ter VLE 


fol Saat Nett TST Te ToT Tela 
COA 
CO ey 





Pe 
GUANO Annee eoeeE 
QALRa, Lowe eReeees 


CO 











Lali 93) 




















attempt was made to ob- 
tain a heat effect with the addition of 1.5% graphite, and in another case 
with 2% coal. The attempts were unsuccessful because these materials 
burned only partially, and also because the heat generated went to heat- 
ing the furnace as well as the clay. 

In the vacuum furnace there is no opportunity for the carbon and sul- 
phur to oxidize and burn, hence these heat effects are lost. It is for this 
reason also that pure clays were selected. 


1 Til. State Geol. Surv., Bull. 9, 284-5 (1908). 


10. 


13 


III. Description of Apparatus 
General Set Up.—The following is a detailed description with 


dimensions of the apparatus. Fig. 8 is a photograph of the apparatus 
ready for arun. ‘The letters correspond with those in the figures. 


(a) 
(0) 
(c) 


Ice Water Tank. A wooden barrel 32 inches deep and 20 inches 
in diameter, heavily lagged on bottom and sides with felt. 

Tube Stirrer. A rotating metal spiral in a copper cylinder 36 inches 
long and 5 inches in diameter. 

Needle Valve. A 1/sinch brass globe valve, set between the ice 





(d) 


Fic. 8.—General view of apparatus. 


water tank and the tube water cooler. With the valve wide open 
and ice water passing through the coils, the capacity is about 1000 
cubic centimeters per minute. 

Tube Water Cooler. A galvanized iron cylinder, 48 inches high, 
10 inches in diameter, containing the copper coils, with false per- 
forated bottom, and with l-inch outlet at bottom. 

Copper Coils. ‘Two coils, about 50 feet each, and */s-inch and 
1/,-inch in diameter, respectively. They are coiled in a close spiral 
6 inches in diameter and for a depth of 30 inches. ‘They are con- 


(e) 


(f) 
(g) 


(i) 


(7) 


(7) 


(k) 


14 


nected at the inflow end with a copper box into which the ice water 
flows from the ice water tank. At the outflow end there is an over- 
flow box, made of copper, 3 inches deep and 3 inches in diameter, 
with the water level at 1!/, inches. ‘The top of overflow box is 
10 inches below the top of the galvanized cylinder, and the box has 
a copper tube extending out of it, to hold the long range zero-degree 
thermometer. | 

Thermometer, 0°, Long Range. Mercury bulb, 1!/, inches long, 
mercury thread 16 inches long to 0° mark. Graduated in 1/1° 
divisions from 0° to 10°. Stem !/,-inch in diameter. Immersed 
in water in box to depth of 11!/. inches. It was compared with a 
standard in ice water, and found to be exact at 0°. 

Drainage Outlet. The outlet for drippings from the ice water in 
the tube water cooler. 

Vacuum Tube. A tube 12 inches long and !/2-inch inside diameter 
was sealed at the ends onto a tube of */,-inch inside diameter, leaving 
an air space between them. This space was evacuated to .002 
millimeters pressure of mercury, and sealed off. The tube con- 
nects the overflow box, through the wall of the galvanized cylinder, 
to the calorimeter bath, through a hole in its side. ‘The tube is 
heavily lagged with felt and covered with oilcloth. 

Calorimeter Bath. An enameled iron bath, 33 inches high and 
22 inches in diameter. It is 29!/2 inches deep from the overflow. 
With the calorimeter in place, the bath will hold 400 pounds of 
water, at 17°. It is lagged with 2-inch felt on sides and bottom, 
and stands on a wooden platform 5 inches above the floor. The 


felt is covered with oilcloth to prevent it from getting wet. 


Bath Cover. ‘This is a galvanized iron cover that fits tightly, 
and is covered with a 2-inch layer of felt. Soldered metal tubes 
in the cover allow for the extension of the stirrer shaft, Beckmann 
thermometer, electric current leads and vacuum connection. _ 
Tube-Stirrer. A rotating metal spiral in a copper cylinder 28 inches 
long and 3 inches in diameter. ‘The stirrer is fastened to the side 
of the bath, and rotates so as to draw the water downwards in the 
tube. 

Electric Current Leads. ‘Three pairs of wires emerge from acentral 
tube in the cover. (1) Heavy wires for the current, (2) light wires 
for the potential leads, and (3) light wires for the thermocouple leads. 
Potentiometer. A Leeds and Northrup instrument with millivolt 
scale graduated in '/;) millivolts. ‘The one hundredths can easily 
be estimated. The two graphs seen next to the instrument are 
(1) the e. m. f. temperature conversion chart, and (2) the deviation 
curve for the thermocouple. 


() 


(m) 


(1) 


(0) 


(p) 


(q) 


15 


Vacuum Connection. A rubber hose connection from the calorim- 
eter in the bath, through a tube in the cover, and connected on 
the outside of the bath to a glass double L. The double 1 then 
connects to (1) Vacuum pump, (2) mercury U-manometer and 
(3) stopcock leading directly to the atmosphere. 3 
Vacuum Pump. A Hyvac pump made by the Central Scientific 
Company. The pump is kept running continuously throughout 
an experiment. } 

Mercury U-Manometer. ‘The long arm was evacuated and sealed 
off. When attached to the evacuated apparatus, the mercury in 
both arms is at the same level. 

Stopcock and Pinchcock. A well ground stopcock with a pinch- 
cock on a heavy rubber hose, to control the pressure in the vacuum 
furnace when necessary. 

McLeod Gauge. Capable of reading to one thousandth of a milli- 
meter of mercury. ‘The gauge is connected to the vacuum pump 
through one arm of a 7, the other arm being connected to the 
double L. 

Beckmann Thermometer. Graduated in one hundredths of a degree. 
The bulb 1'/s inches long and '/2-inch in diameter rests in the water 
in the bath, a few inches away from the overflow. 

Overflow (Bath). As ice water is put into the bath through (g), 
the overflow of the bath escapes through (7). 

Tared Container, Cans with close fitting covers are used to collect 
the bath overflow. 

Rheostats. ‘I'wo plate rheostats in series. A slide wire rheostat 
in parallel with one plate rheostat for fine adjustment. 

Knife Switch. 

Ammeter. O-10 ampere range. Divisions, 0, 1, 2, from 2-10 in 
one-tenths. 

Ammeter. 0-50 ampere range. Divisions, 0, 5, 10, from 10-50 
in '/. units. 

Knife Switch. 

Wattmeter. General Electric Company. Scale 0-500 watts. Am- 
peres 10 and 20, volts 75 and 150, maximum combinations. 

Test Meter. Portable Type IB-5, for alternating current circuits. 
Amperes 1 and10. Volts110. Cycles 60. Two coils, for 1 ampere 
fuse and for 10 ampere maximum through instrument. ‘The instru- 
ment is a revolution counter with three dials. 

Dial (1) reading total of 100 revolutions, divided in 10’s. 

Dial (2) reading total of 10 revolutions, divided in units. 

Dial (3) reading total of 1 revolution, divided in */1o0 revolution. 
When using the 10 ampere coil on the 110 volt circuit, but irre- 
spective of the voltage drop on it, the constant for the instrument 


11. 


(0) 


(c) 
(d) 
(e) 


(7) 





Fic. 9.—Platinum container and furnace parts. 


(z) 
(7) 


16 


is 0.6 watthours per revolution. Maximum load, 10 amperes. 
General Electric Company product. 

Calorimeter Set Up. (Description of Figure 9.)— —(a) Pitta 
Container. Made of 0.004 inch sheet, 8!/, inches high, 1°/s inches 
in diameter, with the bottom end closed, weighing 51.0 grams. 
Alundum Furnace Core. 10 inches long, 11/2 inches bore, !/s-inch 
wall, closed at one end. It has a double thread for holding the 
resistance wire in place—1/¢-inch apart. 

Alundum Cylinder. 10 inches long, 1%/, inches bore, and 1/s-inch 
wall, open at both ends. 

Porcelain Cylinder. Made of a good refractory body, 11 inches 
high, 3 inch bore, and closed at one end. 

Nickel Cylinder. Made of sheet nickel, one millimeter thick, with 
a nickel sheet cap at the bottom. It is just large enough to hold 
the porcelain cylinder. 

Porcelain Upper Support. ‘This is made to fit over the top of the © 


‘nickel cylinder, 3!/, inches to 3!/. inches in diameter, ending in a 


hollow stem, 11!/s inches 
outside diameter and 11/4 
inches high, which fits in- 
to the calorimeter cover. 
(g) Porcelain Lower Support. 
.This is made to hold 
up the nickel cylinder 
in a holder 31/. inches 
in diameter, and 1 inch 
high, the holder termi- 
nating in a slightly 
tapered hollow stem 3 
inches long and tapered 
from 1 inch to 3/4-inch. 
(h) Porcelain Insulator. 
About 6 inches long, 6 
millimeter bore and 2 
millimeter wall, closed at one end. It is imbedded in the material 
held in the platinum container, so that the closed end is situated 
half way down the material and centrally located. 
Porcelain Insulator. 6 millimeter bore and 2 millimeter wall. 
Platinum Resistance Wire. 28 feet long, 0.036 inch in diameter 
and weighing 120.30 grams, wound non-inductively on the core 
(b). Above the core, the ends of the wire are trebled so as to form 
heavy leads for the current, and are encased in the porcelain instu- 
lators. 


17 


Description of Figure 10.—(a) Metal Calorimeter. Made of nickel- 


(0) 


(c) 


plated copper, 14%/, inches high, 73/4 inches inside diameter, and 
1/s-inch wall. It has a bottom screwed in and soldered air tight. 
In the center of the bottom is soldered a hollow metal inset which 
holds the tapered end of the porcelain lower support in place. 
Calorimeter Cover. Made of nickel-plated iron. It slips onto (a) 
snugly to a depth of °/,inch. Its center is cut out and threaded 
to take a 1°/s inch pipe. | 

Heavy Copper Leads. ‘These are connected to the platinum leads 
by means of nickel screw connectors. 





Fic. 10—Metal Fic. 11.—Metal calorim- Fic. 12.—Calorim- 
calorimeter with fur- eter with cover stem show- eter ready to be im- 
nace and thermo- ing excavating tube and mersed in water bath. 
couple lead wires. partially insulated lead 

wires. 


(d) Porcelain Insulators. One millimeter bore and one millimeter wall. 


(¢) 


Thermocouple. Platinum, platinum-rhodium thermocouple, two 
feet long. . 


Description of Figure 11.—(a) Cover Stem. Made of nickel-plated 


(0) 
(c) 


copper, threads into calorimeter cover. It is 41/, inches long and 
has a bore of 11/, inches. 

Copper Evacuating Tube. Made of 5/i-inch stock, and soldered 
into the cover stem about !/,-inch above the calorimeter cover. 
Rubber Pressure Hose. It connects the calorimeter to the vacuum 
pump, by way of the copper evacuating tube. It is coated with 
beeswax to make it air tight. 


18 


(d) Threaded Collar. ‘Iwo inches in diameter, sweated onto the upper 
end of the cover stem. | 

(e) Rubber Stopper. ‘This fits into top of cover stem. 

(f) Glass Tube Insulators. ‘These extend about 2 inches above the top 
of, and 1/s-inch below the bottom of, the rubber stopper, and allow 
the heavy copper leads to pass through, and keep them apart for 
insulation purposes. 

(g) Heavy Copper Leads. The same as shown in Fig. 10. 

(h) Porcelain Insulator. Six millimeter bore and 2 millimeter wall. It 
passes through the rubber stopper and harbors the thermocouple, 
insulating it from the current lead 
wires. One wire of the thermocouple 
is strung with small bore porcelain 
insulators to insulate the two thermo- 
couple wires from each other. 

(4) Current and Potential Leads. ‘To 

/ each heavy copper lead is attached, 

Fic. 13.—Hlectrie wiring set up. by means of a copper screw connector, 
two copper insulated leads, a heavy wire for the current, and a light 
wire, known as the potential lead wire, to be connected to the test 
meter. 

Description of Figure 12.—(a) Copper Extention Tube. Copper Tube, 
91/, inches high and 2 inches in diameter that threads onto the collar 
of the cover stem. It is merely a protection for the wires from 
the surrounding water. 

(b) Water Level. The water in the calorimeter bath reaches to level 
(b). 

12. Electric Wiring Set Up. (Figure 13 Illustrates the Set Up.)— 

(A) Ammeter. O-10 ampere range. : 

(B) Ammeter. 0-50 ampere range. 

(C) Test Meter. Revolution counter. Alternating current only. 

(D) Wattmeter. Indicating wattmeter. 

(EZ) Rheostat. 

(F) Rheostat. 

(G) Electric Furnace. Platinum wound furnace, operated on 110 volt 
alternating current circuit. 





IV. Experimental Data Necessary for Calculating Specific Heats 
In any range of temperature for which a run is made, the following data 
must be known :— 
(1) The electrical energy expended in the resistance furnace. 
(2) The heat absorption of the ice water used to counteract the rise 
in temperature of the bath. 


19 


(3) The temperature of the inflowing.ice water. 

(4) The temperature of the bath. 

(5) The temperature of the material under investigation in the re- 

sistance furnace.. 

The following paragraphs describe the instruments used to obtain the 
above readings, and give their sensitivity and calibration, and all data 
and factors necessary for converting their readings to the purpose at hand. 

13. Electrical Energy.—(a) Portable Test Meter. his instrument, 
of the induction coil type, is essentially a calibrated revolution counter. 
For the 10 ampere coil used in this work, the rating is 0.600 watthour 
per revolution, or 2160 watts per revolution. Allowing 4.186 watts to 
the calorie, gives the meter a value of 516.0 calories per revolution. The 
instrument was calibrated over its full range at 110 volts and found to be 
correct to better than 0.1%. At lower voltages and at the lowest wattages 
used in the experimental work, a comparison with an electrodynamometer 
type of wattmeter gave concordant results to within the Serpe of the 
comparison instrument of 0.1%. 

(b) Indicating Wattmeter. It was found expedient to have an ordinary 
indicating wattmeter in the line, so that the wattage through the furnace 
could be seen at a glance, and easily controlled by means of the resistance 
in series with the furnace. A small amount of current is used in actuating 
the wattmeter, but as it is used in all runs for approximately the same 
wattages and for the same lengths of time, this correction is taken care 
of automatically. 

14. Ice Water Heat Absorption.—(a) Werghing the Overflow. ‘The 
run is started with the bath full and continuously stirred, and with the 
temperature of the bath constant. Ice water is allowed to flow in to keep 
the temperature of the bath constant, as heat is being transferred to the 
water from the calorimeter. The overflow is collected in cans, and for 
any range of temperature, the weight collected is equal to the weight of 
ice water delivered to the bath. ‘The overflow is weighed to a gram. 

Knowing the temperature of the ice water going into the bath, and the 
temperature of the overflow, the heat absorbed in this change in tempera- 
ture is known. ‘The total heat absorption of the ice water for the range 
of temperature can then be calculated. 

Some of the ice water is utilized in counteracting the rise in temperature 
of the bath due to the heat caused by the friction of the stirrer in the bath. 

(b) Ice Water Correction for Stirring Friction. After runs had been made 
on two days several months apart, the bath was allowed to be stirred for 
periods of four hours and the rise in temperature due to stirring noted. 
The increase in temperature amounted to 0.052° per hour. 

On other occasions, the amounts of ice water necessary to lower the 
temperature of the bath 1°, were determined. In one case, 8442 grams 


20 


of ice water cooled the bath from 22.940° to 21.910°, with constant stirring _ 
for 30 minutes. As the raising of the temperature of the bath due to 
stirring is 0.026°, the true lowering of temperature of the bath is 22.940° + 
0.026° — 21.910° = 1.056°. Hence at the average temperature of 
22.425°, it requires 7994 grams of ice water to cool down the bath 1°. 
To counteract one hour of stirring at 22.425° requires 7994 X 0.052 = 
416 grams of ice water. 

At the average temperature of 27.587° it requires 6554 grams of ice 
water to cool down the bath 1°. At 27.587°, one hour of stirring will 
be counteracted by 341 grams of ice water. ‘The ice water used in all 
experiments had a temperature of 0°. 

- By plotting these results the ice water stirring correction for any tem- 
perature of the bath can be found by inspection. 

(c) Heat Capacity of Water. By means of an electrical continuous 
flow method, Callendar! and Barnes* have found the specific heat of 
water over the range of 0° to 100°. Callendar gives the variation of total 
heat h, with the temperature #, in the form of an equation that is of great 
value in the present work, for it is necessary to know the heat capacity 
of the ice water used to keep the temperature of the bath constant. 


4: bes 20 ae t 
h Peele ts log 50 ) 1.1464 GA) + 


0.42 (55) 0.30 (745): 
2 Tepe ee tao 


Thus the heat absorbed by one gram of ice water in changing its tem- 
perature from 0° to 23.560° amounts to 23.709 calories. 

(d) Heat Capacity of the Bath and Contents. From preliminary experi- 
ments it was determined to be 180,440 calories. 

15. Temperature of the Ice Water.—A long range mercury thermometer 
has its bulb in the overflow box of the tube water cooler. It measures 
the temperature of the ice water flowing into the calorimeter bath. The 
thermometer was compared with a French Standard, certified by the 
Bureau of Standards, and was found to be correct at 0°. ‘There is no 
dificulty in having a continuous supply of ice water at 0°, with the ar- 
rangement used, provided constant attention is given to it. ; 

16. Temperature of the Bath.—The temperature of the bath is read 
by means of a Beckmann thermometer graduated in hundredths of a 
degree, and calibrated against a thermometer recently certified by the 
Bureau of Standards. The bulb is situated near the overflow and measures 
its temperature. The temperature of the room is regulated so as to coincide 
with the temperature of the bath to within a few tenths of a degree. 


1H. L. Callendar, Proc. Roy. Soc. (London), 86A, 254-7 (1912). 
2H. T. Barnes, Trans. Roy. Soc. (London), 199A, 149-263 (1902). 





21 

17. Temperature of the Material in the Furnace.—The junction of a 
two-foot platinum, platinum-rhodium thermocouple is imbedded in the 
center of the material which is being heated in the furnace. The two 
ends of the couple extend one inch above the top of the cover of the calo- 
rimeter bath. ‘They are connected toa Leeds and Northrup potentiometer 
by copper leads. A thermometer hanging just above the bath measures 
the cold junction temperature, which is corrected in the temperature 
measurements. The thermocouple and potentiometer were calibrated 
against the freezing points of pure metals supplied by the Bureau of Stand- 
ards for such work, and the deviations in temperature were plotted as . 
suggested by Adams.! | 


V. Heat Insulation 


18. Furnace Insulation——From preliminary work, it was found that 
the heat loss from the furnace had to be reduced as far as possible. ‘The 
advantage in decreasing the input of electrical energy was in increasing 
the fraction of heat expended on the material. This was accomplished 
(a) by running the furnace under 
vacuum conditions instead of at 
atmospheric conditions, and (b) by 
packing the furnace core with a 
good insulating material. In order 
to reach 1100° under atmospheric 
conditions, about 750 watts from a 
12-15 ampere current had to be 
expended, whereas with the present 
vacuum furnace, 350 watts from an 
8-ampere current will give 1200°. 
The maximum current capacity of 
the test meter is 10 amperes. 

It has been found that fused zirco- 
nia has the lowest specific heat 
(0-100°, 0.1075)? and heat conduc- Daag Pao a RCOMRS EOE D00% “Pee 
tivity (about 0.00039)? of any ma- ate Pagel t se 
‘terial suitable for furnace packing. Fic. 14.—Heat capacity of ae of quartz 

10). Bath Insulation.’The calo- calculated from White’s results. 
rimeter bath is covered on its sides, top and bottom with two-inch felt to 
minimize heat exchange with the room. The temperature of the room 
was kept to within a few tenths of a degree of the temperature of the 
































Calo mies 



























































1ZTeason H. Adams, “Symposium on Pyrometry,” Am. Inst. Mining Met. Eng., 
165-78 (1920). 

2 J. W. Marden and M. N. Rich, Bur. Mines, Bull. 186, 20 (1921). 

3. S. Hutton and J. R. Beard, Proc. Faraday Soc., 1, 266 (1905). 


22 


bath so as to minimize the radiation exchange. ‘The felt is covered with 
oilcloth to prevent it from getting wet. 

20. Insulation for the Ice Water System.—The ice water tank and 
the tube water cooler are covered on all sides with two-inch felt. 

The valve and pipe connections between the ice water tank and the tube 
water cooler are very heavily covered with felt. ‘The connection between 
the tube water cooler and the bath is a vacuum tube, which is also well 
covered with felt and oilcloth. The vacuum tube, set at an angle of 30°, 
is connected by rubber hose to the overflow box in the tube water cooler, 
and leads the ice water directly into the tube stirrer in the bath by means 
of another piece of rubber hose. 


VI. Preparation for an Experiment 


All of the parts of the apparatus mentioned in this chapter are described 
in Chapter II, and are illustrated in the figures accompanying it. 

21. Preparation of the Sample.—If the material is inert like quartz, 
the crushed particles are filled 
into the platinum container. 
‘is irae ‘| Ifthe material is a clay, which 
| is finely divided and contains 
150000 is water of combination, it must 
T first be molded. 
| The clay is made to pass a 
20-mesh screen, and _ then 
worked with water until a 
plastic mass is obtained. The 
mass is then put into a screw 
press and forced through a 
1'/o-inch orifice. The stiff 
column is cut up into pieces 1 
to 2 incheslong. Half of these 
pieces are then centrally bored 

: 5 = 7 with a 5/;s-inch cork borer. All 
Degrees Centigrade of the pieces are allowed to dry 

Fic. 15.—Quartz runs and heat capacity of at 110° over night. ‘The solid 
system in range 23.560-420°C. Heat capacity pieces with a total length of 4 
of system 23.560- 00° = 142,400 calories. : ; 

inches are trimmed down to fit 
the platinum container snugly. The hollow pieces are trimmed down to fit 
the container, and are also hollowed out to allow the porcelain thermo- 
couple protection tube to slide through them. ‘The container is then 
filled up with these hollow sections, and the protection tube is slipped 
into place. 


€00000 














=e 




















100000 





Calories 

















50000 
























































23 


22. Assembling the Calorimeter.— The platinum container and its 
charge are then slipped into the furnace core, so that it stands on the false 
bottom consisting of a thin alundum disc resting on a porcelain ring. 
The furnace core is slipped into the alundum cylinder, which is surrounded 
by the zirconia packing, held in place by the porcelain cylinder, with the 
nickel cylinder on the outside. The weight of the furnace parts are:— 


Grams 
Miceeland porcelain cylinders: fa. /H.. e ee n. 1406.0 
BateOltinepa CKiIngte irc. ry tee ant eae ee ee he 1321.0 
CCIAMIN eV Ine: anes de Pak f. cs he. Lime em 220.8 
PRUETT COLE UTED a oO or gee, Jet SO NE ie one ee 205.3 
IRACMINID CON LAGr = sae Oa, Were My Ae aCe oe te ee 51.0 


The nickel cylinder and contents are now ready to be set onto the porce- 
lain bottom support which is in its holder in the base of the metal calorim- 
eter. The porcelain upper sup- 
port is now put on, and then 
the metal cover of the calorim- 
eter is forced on. 

The lead ends of the platinum __,,,,,. 
resistance wire are now sheathed 
with the porcelain protection 
tubes, and are attached by 
nickel screw connectors to two 
bare heavy copper leads. The 
cover stem, provided with a roll 
of dehydrated mica that fits 
snugly on the inside, is then Foy 
slipped over the copper lead 
wires and screwed into place, a 4 
thereby holding the porcelain io 
upper support in position by eciall irae aaa 
its extension below the cover. Degrees Centigrade 

A rubber stopper fitting into Fic. 16.—Heat capacity of A-I English china 
the cover stem carries in it two clay 247.5 grams in range 24-420°C. VI, 
short glass tubes through which 23.560-422° = 41,400 calories; IX, 23.560- 

. 415° = 41,000 calories. 

the heavy copper leads can just 

pass, and also carries a porcelain protection tube through which the 
thermocouple wires are led. When the rubber stopper is in place, its 
porcelain protection tube just touches the porcelain tube that is inserted 
in the material. The thermocouple is now inserted into place, its two 
wires being insulated from each other by small porcelain insulators. ‘The 
- copper lead wires are strung with glass tubing and are held in position 
so that there can be no short circuiting. 


200000 

























































Calories 





ee 


ace 
| SeSe a 


















































24 


The two openings through which the lead wires enter the glass tubes in 
the stopper, and the openings whereby the thermocouple wires enter 
the porcelain protection tube, are now sealed with De Khotinsky cement. 
All other joints are made vacuum tight by painting them with a heavy layer 
of beeswax. ‘To each heavy copper lead are attached by means of a copper 
screw connector, the two lengths of insulated copper wire. The screw 
connectors are insulated with rubber tape. ‘The copper extension tube 
is now slipped over the 
four insulated lead wires 
and over the separately 
insulated thermocouple 
wires, and threaded into 
place. The joint is made 
water tight with a layer 
of beeswax. ‘The appa- 
ratus is clamped into its 
metal frame and is ready 
for immersion in the 
bath. 

23. Evacuating the 
Calorimeter.—The calo- 
rimeter bath is filled with 
water and the calorim- 
eter set in the middle 
of it. ‘The cover is put 
on so that the six wires 
from the calorimeter pass 
directly through the cen- 
tral tube. The rubber 

400 550 700 850 700 +=. ose. attached to the calo- 
OSI RES oe eRe rimeter is connected to 
Fic. 17.—Heat capacity of A-I English china clay the vacuum pump. 


247.5 grams range 400-900°. VI, 421-900° = 121,200 
calories; IX, 421-900° = 103,200 calories. 


300000 



































200000 























/50000 








Calories 














/00000 




















50000 













































































The lead wires are con- 
nected to the source of 
current and the instruments, and the thermocouple wires are connected 
to the potentiometer. 

Thevacuum pump is started and thesystem is evacuated for several hours, 
to get rid of adsorbed air. The pressure is then usually below a millimeter. 
The pump is then shut off, and the system allowed to remain evacuated. 

24. Ice Water Supply.—On the day before a run is to be made, the ice 
water tank is filled with water and crushed ice and stirred continuously. 
The tube water cooler is filled with crushed ice. From time to time the 
ice is Shaken down and packed around the coil to insure intimate contact. 


25 


This process of packing and refilling is made every half hour during the 
run. The thermometer in the overflow box records the temperature of 
the ice water. During the run, the ice water tank is frequently supplied 
with water and ice, to keep the head of water on the valve constant. Usu- 
ally about 600 Ibs. of ice are sufficient for the complete run. 


VII. Experimental Procedure 


25. Ascending Temperatures—When the calorimeter bath is stirred 
and filled just to overflowing, and the temperatures of the bath and room 
are the same, with the ice water supply at 0°, and the vacuum pump work- 
ing smoothly, the test meter is read and a tarred can placed under the over- 
flow. The current is turned on, and the resistance in the circuit varied 
to give the required wattage through the furnace. ‘The wattage is con- 
tinuously watched and kept 


450000 
constant, for from prelim- H 
inary work it is known that Fe 








a Aue 








this wattage will raise the Y 
VAN 
HY 


furnace temperature the re- 
quired amount. ee eee 
The temperature of the 
bath is kept constant by 
varying the ice water flow 
into the bath. Normally 
the fluctuation of the tem- 
perature can be controlled 
to +0.01°. The test meter 
readings are-recorded. If = 0000 ae ae 
the material being heated’ - pee as es Ee 
is a clay, the pressure de- Wegeee®, Sen URE 
veloped in the furnace is Fic. 18—Heat capacity of A-I English china clay 
recorded with the cor- 2/62 grams in range 900-1200°C. IX, Ascend- 
ing temp. (a) 892-1187° = 5,200 calories. De- 


responding temperature of scending temp. (d) 1187-892° = 12,200 calories. 
the clay. If the substance 


being heated is an inert material like quartz, a pressure in the calorimeter 
is artificially developed by working the pinchcock attached to the stop- 
cock tube in one arm of the double L-tube in the vacuum system. 
The pressure curve followed is that of the clays at corresponding tempera- 
tures, thus making the heat insulation for the quartz run equivalent to 
the heat insulations found for the clay runs. 

When equilibrium has been attained, that is when the furnace tempera- 
ture has reached its maximum, the exchange of heat between the calorim- 
eter and the ice water inflow is balanced. In practice, the equilibrium 
is considered to have been attained, when the rise in temperature of the 























Cayorres 





























26 


furnace, in the neighborhood of the maximum temperature, is even and 
very slow, in the order of !/2° a minute. When this stage has been 
reached, the furnace temperature and test meter readings are recorded, and 
the overflow can replaced by an empty one, as soon as the temperature of 
the bath coincides with the initial temperature of the run. The wattage 
is then increased and the procedure repeated for the second range of the 
run. : 

The data obtained are then the total electrical energy consumed in the 
furnace, the total weight of ice water used, and the temperature to which 
the material has been heated. ‘The weight of the material, the tempera- 
ture of the ice water and of the bath, are already known. Similar data 
are found for each stage of the run. 

With clays the main dehydration period exists between 420° and 900°, 
making it necessary to have this range all in one stage of the experiment. 


This then limits the run 
Ee al aa i ek 


to three stages for the 
See aa ffs 


ascending temperatures. 
BOREL, ay aren 














100000 


With 90-110 watts 420° 
can be reached” in@ the 
furnace; then increasing 
to 200-240 watts will raise 
the temperature to 900°, 
and finally increasing to 
300-350 watts, will give 
1200° as the maximum 















Calories 
Q 
9 
9 
9 
9 








He, temperature. 
ra) e 
Sti pis. 26. Descending Tem- 
600 660 720 300 peratures.—At the end of 


D Centigrad i 
egrees Centigrade the last ascending tem- 


Fic. 19.—Heat capacity of A-I English china clay perature range, when equi- 
216.2 grams in range 900-700°C. IX, 912-679° = librium has been reached, 
1300 Sania: the current is cut off, and 
the heat given up by the calorimeter to the bath is balanced by ice 
water. ‘The temperature falls fast and continuously. 

The descending run is divided into two stages, roughly 1200-900°, and 
900-700°, the only data being obtained, are the quantities of ice water 
used for each descending range of temperature. 


VIII. Heat Capacity of the ‘‘System”’ 


27. Heat Capacity of Quartz.—The quartz used in the calibration runs 
was a Baker and Adamson product of crushed crystals, analyzing 99.98% 
5102, and having indices of refraction 1.544-1.553, and a specific gravity 
of 2.654. 


27 


The heat capacity of the quartz was calculated from the results of 
White,* in Fig. 1, to give the values for one gram of quartz as repre- 
sented graphically in Fig. 14. By plotting a similar curve for 251 grams 
of quartz, the weight used in the calibration runs, the heat capacity of 
the quartz between any two temperatures in the ranges 24—420°, 420- 
900°, 900-1200°, 1200-900°, and 900-700°, can be easily obtained and 
used for deriving the heat capacity of the “system.” 

28. Heat Capacity of the “‘System.’’—Several calibration runs were 
made with the quartz, and the net heat absorbed in raisirig the temperature 
of the quartz and the “‘system’’ through the ranges mentioned above were 
calculated from the data on electrical energy input, the quantity of ice 
water used to keep the temperature of the bath constant, and from the 
stirring-friction ice water correction. ‘These results of the net heat ab- 
sorbed, in all of the ranges of temperature for the calibration experiments, 
do not differ in duplicate runs by more than +1%. ‘The steps in the calcu- 
lations are very similar to those made for the clays. 

The net heat absorptions obtained in each temperature range are plotted 
with the calculated heat absorption for the quartz, an example being given 
in Fig. 15. The experimental data curves are marked with Roman 
numerals. In most cases the initial temperatures in the various ranges 
covered by the calibration runs and by the experimental clay runs are 
different, and for calculating purposes their corresponding curves have to 
be transposed parallel to themselves to pass through a common origin. 
Such transposed curves are marked “‘tr’’ on the figures. Where distinc- 
tion has to be made between ascending and descending temperature curves, 
they are accordingly designated ‘‘a’” and “‘d’”’ on the figures. 

By subtracting graphically the calculated heat absorption of the quartz 
from the heat absorption of the combined quartz and “system,” determined 
experimentally, the heat capacity of the “system’”’ is obtained, and its curve 
is marked accordingly. 

These “system” curves are then used for obtaining the heat absorption 
of the clays, by subtracting them from the net heat absorption values, 
determined experimentally for the clays and the “system” in the requisite 
ranges of temperature. ‘The resultant data are: 


Heat Capacity oF THE “SYSTEM”’ 


‘Temperature range Calories Cal. per 1° 
23 . 560-—400° 142,400 379 
421-—900° 170,079 355 
( . 
ascending and 

— “ 109,778 372 

SEI | descending 
892-679° 65,317 307 


1W. P. White, loc. cit. 


28 


IX. Experimental Data for the Heat Absorbed and Evolved by Clays 
during Firing and Cooling 
29. A-1 English China Clay.—The following are the detailed experi- 
mental data and the resulting calculations for duplicate runs VI and IX, 
made on 247.5 grams of air dried A-I English china clay: 


(a) Range 24-420° 


Run Temp. interval 
VI 23 . 560—422° 
IX 23 .560-415° 


Energy input 


The net heat energy used is then obtained: 


Run Temp. interval 
VI 23 .560—422° 
IX 23 .560-415° 


Ice water, Duration 
Revolutions grams in hours 
461.30 3,086 2.93 
452.70 2,954 25 
Energy in calories 
Electrical Ice water Net 
238,030 45,379 192,651 
233,594 43,956 189,638 


The net heat energy absorbed is represented in Fig. 16 as the upper 
curves marked VI and IX. ‘The curve marked “system” is transposed from 


the quartz calibration curves. 


By subtracting the “system” curve from 


the upper curves, the lower curves are obtained, these representing the 


heat absorbed by the clay alone. 


Run Temp. interval - 
VI 23 .560-422° 
TX 23 .560-415° 


(b) Range 420-900° 


Run Temp. interval 
VI 422-894° 
IX 415-895° 


The net heat input is: 


Run Temp. interval 
VI 422-894° 
IX 415-895° 


Numerically the data are: 


Heat absorption in calories 


Total Per gm. per deg. 
41,400 0.420 
41,000 0.423 


—_—_ 


Av. 0.422 + 0.002 


Energy input 


Ice water, Duration 

Revolutions grams in hours 
2748.00 50,956 8.33 
2787 .00 52,217 7.80 

Energy in calories 
Electrical Ice water Net 

1,418,000 ‘1,129,200 288,800 
1,438,100 1,164,000 274,100 


. The curves for the net energies are given in Fig. 17. The net results 


differ from the average value by +3%. 


are: 


‘The values for the heat absorbed 


Heat absorption in calories 


Run Temp. interval Total Per gm. per deg. 
VI 421-900° 121,200 1.022 
IX 421-900° 103,200 0.871 


Av. 0.947 + 0.075 


29 


(c) Range go00-1200° 
Energy input 


Ice water, Duration 
Run Temp. interval Revolutions grams in hours 
Via 894-1186° 774.82 12,606 “1,42 
IXa 895-1187° 897.53 15,402 1.68 
IXd 1187-912° Pak. 5,025 0.55 


These results may be summarized: 


Energy in calories 


Run Temp. interval Electrical Ice water Net 

Via 894-1186° 399,810 235,410 114,400 
IXa 895-1187° 463,130 349,230 113,900 
IXd Si-O 1D cae Ata oe 113,920 113,920 


The curves corresponding to the net energy consumption are given in 
Fig. 18. 

Between 892° and 1186° the ascending curves VIa and IXa vary only 
by 500 calories in 115,000, or a difference of +0.21%. On subtracting 
the heat absorption for the “system,” the total heat absorptions for the 
clay differ by 500 calories, which now represents a difference of +4.6%,. 

The weight of the dehydrated material in run VI was 216.8 grams and 
in run IX 216.2 grams corresponding to losses of weight of 12.40% and 
12.65%, respectively. ‘The heat absorption and evolution are calculated 
per gram of air dried clay, and per gram of dehydrated clay. 


Heat absorption in calories 


Per gram Per gram 
air-dried clay dehydrated clay 
Run Temp. interval Total per deg. per deg. 
Via 892-1186° 5,700 0.078 — 0.089 
IXa 892-1187° 5,200 0.071 0.082 
Av. 0.075 0.086 
+0 .004 +0.004 
Heat evolution in calories 
IXd 1187-892° 12,200 0.167 0.191 
(d) Range goo-700° 
Energy input 
ice water, Duration Net heat 
Run Temp. interval grams in hours in calories 
IX 912-673° 4,136 0.75 90,948 


The corresponding curve is given in Fig. 19: 


Heat evolution in calories 


Per gram Per gram 
air dried clay dehydrated clay 
Run Temp. interval Total per deg. per deg. 
IX 912-679° 17,500 0.303 0.347 


(e) Average Heat Absorption and Heat Evolution 
To heat 1 gram of air-dried A-I English china clay from 25° to 1200° 


requires 644 calories. 


30 


'VABLE. cl Vi 


HkEAT ABSORBED AND EVOLVED BY CLAY DURING FIRING AND COOLING 
(For the first two clays the values given are the average results of two independent experiments and the deviations from this average are 














indicated) 
Dehydration period 
Specific Period of Pres- 
Loss on Heat absorbed per gram per Heat evolved per heat of the Pres- maximum sure 
ignition, degree on heating the air-dried (110°) degree on cooling the re- fired clay sure _ pressure, falls to 
Clay type per cent clay over the temperature ranges given sulting quantity of fired clay cal./gm., rises 20 mm. 3 mm, 
25-420° 420-900° 900-1200° 25-1200° 1200-900° 900-700° 1200-700° 1200-700° 
NG Car. ek aolinen hae 14.0 0.49 0.69 0.23 0.50 0-23 0.28 0.24 0.28 25 S460 seee) (Oa 
to to to 
—0O.07 +=0.05 =+0.01 =0.0835 +0.01 +0.06 +0.05 +0.05 460° 570° 780° 
A-1 English China... . 12.5 0.42 0.95 0.075 0.55 be hg 0.31 0.20 0°23 2024 450 - gots 
to to to 
=0.01 +0.07 +=0.004 +0.07 480) SADR = 7602 
Tenn. Ball No. 5..... 13.8 0.47 0.53 0.51 0.51 0.20 0.33 0°25 0.29 PAS, Laie ROR 550° 
to to to 
4700 te 55032 as SOO" 
Laclede-Christy Raw 13.0 0.47 0.68 0.24 0.50 Os17 0:37 0.25 0.29 205 4 (USE GoUe 
Hint ee to to to 
A702" 2 630 SRR 5Oe 
A VeCTARee hae Se 0.46 0.51 0.19 0.82 0.24 0.27 


ol 


Temp. interval Calories 
25-420° : 395 X 0.422 &* 1.00 = 167 
420-900° 480 X 0.947 K 1.00 == 455 
900-1200° 300 X 0.086 X 0.87 = 22 
Total 644 


The average heat absorption per degree for A-I English china clay 
between 25° and 1200° is then 0.55 calories. | 

One gram of A-I English china clay, heated to 1200°, will evolve heat, 
on cooling, as follows: 


Temp. interval Calories 
1200-900° 300 X 0.191 X 0.87 = 50 
900-700° 200 X 0.347 X 0.87 = 60 
Total 110 


or an average heat evolution of 0.22 calories per degree between 1200° 
and 700°. 


30. Tennessee Ball Clay No. 5.—250.9 grams of air-dried clay were 
used, the results being givenin Table IV. ‘The heat absorbed in the ascend- 
ing temperature range 900-1200° was large, part of the heat being ab- 
sorbed by gaseous reactions. This assumption is substantiated by the 
gas pressure developed in the furnace, the foul smell of decomposed organic 
matter issuing from the vacuum pump, and the black appearance of the 
burned clay indicating organic matter. 

31. North Carolina Kaolin.—Duplicate runs on 219.6 grams of clay 
were made, there being no unusual features to record. 

32. Laclede-Christy Raw Flint Clay.—303.4 grams of clay were em- 
ployed. A small gas pressure was developed in the ascending temperature 
range 900-1200°, probably explaining the increase in heat absorption as 
compared with the heat evolution in cooling over the same range of tem- 
perature. 


- X. Summary and Conclusions 


The numerical results obtained are displayed in Table IV. ‘They repre- 
sent the data obtained for four types of clays. 

33. Conclusions.—The following points and conclusions are brought 
out by the data presented in the table: 

(1) All four clays contain approximately the same amount (14%) 
of moisture in the air dried condition. 

(2) During the initial period of heating (up to 420°), in which all of 
the hygroscopic and some of the chemically combined water is driven out 
all of the clays absorb approximately the same amount of heat, 0.46 calories 


per gram per degree. 


o2 


(3) Between 420° and 900° the remainder of the chemically combined 
water is driven out, most of it between 470° and 600°. During this period 
two of the clays, the North Carolina kaolin and the flint clay, show the 
same heat absorption, about 0.7 calorie per gram per degree. ‘The other 
two clays behave differently, the English china absorbing 0.95 and the 
Tennessee ball only 0.53 calorie per gram per degree. 

(4) During the final or finishing period 900° to 1200°, the North 

Carolina kaolin and the flint clay again exhibit similar behavior, each 
absorbing about 0.2 calorie per gram per degree. The English china 
‘clay, however, absorbs only 0.075 calorie per gram per degree over this 
range: Since this is less than the specific heat of the fired clay (0.17) 
in this temperature range, it shows that some reaction is taking place which 
evolves heat. Over the same range the Tennessee ball shows a heat ab- 
sorption of 0.51 calorie per gram per degree and by a similar process of 
reasoning this clay is evidently undergoing some reaction which absorbs 
heat. : 

(5) Over the whole firing period all four clays behave alike as regards 
the total heat which they absorb during the firing operation, the heat 
absorption amounting to 0.5 calorie per gram per degree. 

(6) Stated in another way, the amount of heat which must be put into 
the clay ware in order to completely fire it, if the finishing temperature 
is 1225° amounts to 1200 X 0.5 or 600 calories per gram of bone dry 
body. 

(7) If, however, the heat content of the fired ware is utilized during 
cooling (as, for example, to heat the air for a drier) the net heat required 
by the various reactions which occur in the clay during the firing opera- 
tion is 1200 X (0.51-0.24) or 320 calories per gram of bone dry body; 
or, stated in another way, 1 gram bone dry clay at 25° = 0.86 gram fire 
clay at 25° + 0.14 gram water vapor at 25°-320 calories. 

(8) If we subtract from these 320 calories the heat required to vaporize. 
the 0.14 gram of water present (2. e., 77 calories), the remainder, about 
240 calories, represents the heat absorbed by the dehydration reaction 
(at room temperature to produce liquid water) plus the net heat absorbed 
by all of the other chemical reactions which occur during the firing (also 
at room temperature). 

(9) The results given above supply for the first time reliable data on 
the heat absorption of clay in a form suitable for use in heat-balance calcu- 
lations. 

(10) No attempt has as yet been made to correlate the above results 
with the burning behavior of these clays. 

The results here presented of course apply strictly only to the four clays 
investigated. Moreover, they should be looked upon as the initial results 
in an entirely new field of investigation. ‘They represent a new type of 


30 


calorimetric work and their principal value is the indication which they 
give of the possibilities in this field. 

Incidentally it may be pointed out that the calorimetric method de- 
veloped in connection with this investigation can be used to determine 
the heat effects of other high temperature processes such, for: example, 
as the heat of fusion of a glass batch or the heat absorbed in manufacturing 
cement clinker. 

34. Acknowledgments.—The problem was suggested by Dr. E. W. 
Washburn, who devised the method, and under whose supervision the 
major part of the work has been done. ‘The writer sincerely appreciates 
the inspiration of his teacher, an inspiration which has proved itself a 
great influence in promoting interest in research work. 

The investigation was part of a codperative program of work undertaken 
by the Joint Research Committee of the Four Heavy Clay Products 
Associations, the United States Bureau of Mines, the United States Bureau 
of Standards, and the joint committee on Ceramic Research of the National 
Research Council and the AMERICAN CERAMIC SOCIETY. 

NotEe:—Acknowledgment is due to the United States Bureau of Mines whose 
valued financial aid made this investigation possible, and to the Engineering Experi- 
ment Station of the University of Illinois for.apparatus and facilities put at the writer’s 
disposal: The work was completed under Prof. C. W. Parmelee, who furthered the 
investigation with his keen interest and guidance. 


VITA 


The writer was born in Grodno, Russia, on September 9th, 1897. 

He received his education, through high school, in Johannesburg, South 
Africa, matriculating from King Edward VII School in 1913. 

In the Summer of 1914, the writer attended. the Columbia University. 
He transferred to the College of the City of New York, graduating in 
1918 with the B. S. degree in Chemistry. 

For two years, 1918-1920, he was employed in the Glass Plant of the 
Bausch and Lomb Optical Company, Rochester, New York, doing analy- 
tical and research work in connection with optical glass. 

In 1920 the writer came to the University of Illinois for graduate work. 
He was a Fellow for the two years, 1920-1922. He received the M.S. 
degree in Ceramic Chemistry in 1921. He was made an active member 
of Sigma Xi in 1921. 

The following are the writer’s publications: 

“The Products of the Calcination of Flint and Chalcedony.” Edward 
W. Washburn and Louis Navias. Journal of the American Ceramic 
Society. Volis, ps p00-oG0, 11922): 

“The Relation of Chalcedony to the other forms of Silica.’”’ Edward 
W. Washburn and Louis Navias. Proceedings of the National Academy 
of Sciences. Vol. 8, p. 1-5, (1922). 


+ ge 
A Ned 
RP 
oe 




















| anes 3.0112 059245610, 
: 
:: 
ie 








